1. Field of the Invention:
The present invention relates generally to a rotary drafting apparatus for use in a spinning machine, and more particularly to a rotary drafting apparatus of the type in which a rotary gill or chain gill has its sliver control members made always rotatable at a predetermined angular velocity.
2. Description of the Prior Art:
A chain gill, a rotary gill or the like is conventionally usable in a rotary drafting apparatus. Since the sliver control members are used in the rotary drafting apparatus, for instance, chains or control rollers are usually driven by a gear mechanism, they will be rotated temporarily at an angular velocity excessively higher than a predetermined level as a result of sudden increase in the drafting force of the front rollers owing to the condition of the sliver and the like. Thus, the conventional drafting apparatus has a disadvantage that the spinned sliver obtainable has a non-uniform or uneven thickness.
In this connection, the rotary drafting apparatus of the inventors, as disclosed in Japanese Patent Publication No. 67-6016, could accomplish the combing treatment of the sliver more efficiently and uniformly than the prior-art apparatus. However, the unevenness in the thickness of the sliver could not be completely eliminated even by this apparatus.
We, have studied the causes for the formation of uneven sliver, and discovered that the unevenness comes mainly from the fact that the sliver control members closer to the front rollers are caused to undergo, as a result of temporarily excessive drafting force of the front rollers, correspondingly increased angular velocity excessively higher than a predetermined level which is regulated by the driving mechanism. In the conventional drafting apparatus, the driving force from a prime mover is usually transmitted to the back gears, which are coaxially secured to the back rollers, by way of a reduction gear mechanism, and then to the front rollers by way of several intermediate gears and coacting gears which are coaxially secured to control members such as the control rollers. In the power transmission gear mechanism of this kind, however, the accumulation of the clearances or backlashes of the associated gears are so great that they are rotated temporarily at an excessive angular velocity by the temporarily excessive drafting force of the front rollers. This excessive rotation is a major cause for the unevenness in the obtained sliver.